P01F1
O2 Sensor Circuit Bank 1 Sensor 4
Generic electrical fault on the bank 1, sensor 4 oxygen sensor (fourth sensor downstream — used on systems with multiple cat stages or NOx-trap diagnosis).
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
Ordered by how often each turns out to be the cause.
- Sensor failedCommon
Parts involved
- Oxygen Sensor B1s4
- Sensor Wiring
P01F1 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.